Endoscopes are mainly used for visually examining the esophagus, the stomach, the intestine (from the stomach or from the anus), the urethra and the bladder. For this purpose, the endoscope is equipped at its distal end with a lighting device and with an optic, preferably a camera chip, which is connected via leads inside an endoscope shaft to a camera control means at the end of the endoscope shaft. The camera control means is in turn connected via a video processor to an external monitor on which the operating physician can identify the areas to be examined. The distal end of the shaft to be introduced into the cavity is here designed so that it can be bent in any direction, and it can be angled, much like a finger, manually by means of a handle, preferably via two control wheels with brake at the rear end section of the endoscope. In addition, the endoscope shaft generally has at least two channels passing through it, and opening out at the frontmost point of the distal end. When so required, these channels can be used for passing though cleaning fluid, for example, in order to clean an area which is to be examined, or CO2 (air) for opening out the cavity, or else various working instruments can be pushed through a working channel, for example forceps or scissors for removing tissue specimens, biopsy needles, heatable cutting wires, coagulation electrodes, which can likewise be manually operated at the rear end of the endoscope shaft via operating wires or Bowden cables inside the inner channel. When removing a tissue specimen, after the distal end has reached the location in question, forceps for example are introduced into the channel from the direction of the rear section of the endoscope shaft and are advanced to the distal end. After the specimen has been removed, the forceps are drawn back again and removed from the channel so that further examination can be continued.
The endoscope generally has an elongate tubular shape, with a diameter of about 9 to 15 mm, and consists of a flexible material so as to be able to follow the curvatures of the cavity which is to be examined, for example intestinal loops.
An endoscope of this generic type is presently known from the prior art, for example in accordance with DE 4,242,291 A1.
This endoscope essentially consists of an endoscope head or distal end, which is adjoined by an endoscope shaft consisting of a flexible bendable tubular body, and an operating mechanism at the rear end of the endoscope shaft. The operating mechanism has a number of operating wheels which are mounted rotatably on the endoscope shaft and which are operatively connected to the distal end via operating wires or Bowden cables which are run through the inside of the endoscope shaft. Moreover, in a rear end section of the endoscope there is provided a first drive or advance mechanism which exerts a driving force on the endoscope shaft via drive wheels.
Arranged around the endoscope shaft, at least in its front section, there is a roll-back tube which is driven by a second drive or advance mechanism. The roll-back tube here consists of an inner tube section which bears slidably on the jacket surface of the endoscope shaft and is turned back in the area of the distal end of the endoscope to form a front outer tube section. The front outer tube section is also guided back as far as the second drive mechanism and fixed to the housing thereof. In the rear area of the endoscope, the inner tube section is turned back to form a rear outer tube section, which is likewise guided to the second drive mechanism and fixed to the housing thereof, on the axial end side directed away from the front outer tube section.
The second drive mechanism here acts on the inner roll-back tube section in order to move the latter in the axial direction of the endoscope shaft. For this purpose, the second drive mechanism has a type of cuff or collar which can be contracted in the radial direction and thus pressed with friction onto the inner tube section and can also be moved in the axial direction of the endoscope in the manner of a piston. The radially acting pressing force of the cuff is in this case chosen to be so great that at least some of the applied pressing force is transmitted, by a material deformation of the inner tube section, to the jacket surface of the endoscope shaft, so that the endoscope shaft is driven together with the inner roll-back tube.
Since, with this type of drive alone, effected by the second drive mechanism, the speed of advance (and travel) of the roll-back tube at its front roll-back area would, because of its roll-back movement, be only half as great as that of the endoscope shaft, i.e. the endoscope shaft would, with increasing depth of penetration, emerge telescopically from the roll-back tube, the first drive mechanism, mentioned in the introduction, exerts a braking force on the endoscope shaft, which braking force counteracts the advancing force of the second drive mechanism.
The second drive mechanism is in this case synchronized with the first drive mechanism in such a way that, in the interaction of the two drive mechanisms, the speed of movement of the inner tube section in an axial direction is twice as great as the speed of movement of the endoscope shaft, this sliding relative to the inner endoscope shaft (i.e. the distal end of the endoscope shaft moves at the same speed as the turn-back area of the roll-back tube).
In order to facilitate the relative sliding movement between the endoscope shaft and the roll-back tube, the prior art according to DE 4,242,291 A1 further provides a lubricating device by means of which a lubricant can be forced in between the inner tube section and the endoscope shaft and also between the inner and outer tube sections. For this purpose, the lubricating device has a cone-shaped sleeve which is slipped over the endoscope shaft and interacts sealingly with the rear roll-back area of the roll-back tube, which rides up onto the cone-shaped sleeve. The lubricant, which is forced by means of a pump into the gap between the cone-shaped sleeve and the endoscope shaft, spreads out between the inner tube section and the endoscope shaft along the entire length, and excess amounts of lubricant in the front turn-back area of the roll-back tube emerge into the cavity which is to be examined.
It has now been shown that the endoscope according to DE 4,242,291 A1 has, particularly in respect of the driving of the roll-back tube and the endoscope shaft, and also in respect of the relatively high losses of lubricant through leakage in the front turn-back area of the roll-back tube, certain faults which make the use of the endoscope difficult.
Thus, in particular, the above-described second drive mechanism proves to be disadvantageous, since the pressing force which is transmitted over a large surface area from the cuff to the endoscope shaft, via the elastically deformed roll-back tube, leads to a considerable impairment of the relative slidability of the endoscope shaft inside the roll-back tube, despite the admission of lubricant. To this extent, an increased braking force has to be applied to the endoscope shaft by the first drive mechanism in order to maintain the speed ratio between roll-back tube and endoscope shaft of 2:1. Moreover, the first advance mechanism can be synchronized only with some difficulty, and thus cost, with the piston-like advance movement of the second advance mechanism. It is thus evident that the first drive mechanism not only has to be dimensioned to give high output, and accordingly also be of large design, but also that a greater control outlay is entailed. Moreover, the piston movement the little suited to positioning the distal end exactly at a location which is to be examined.
It is known from a further prior art, in particular according to DE 3,925,484 A1, to design the distal end of the endoscope shaft with a mushroom-shaped head piece having a concave sealing surface which is directed toward the roll-back area of the roll-back tube and which, as the roll-back tube is being driven, is in sealing engagement with its roll-back area. However, this design necessitates a widening of the endoscope shaft, in particular of the distal end, and thus once again to impaired handling of the endoscope.